Operation of centrifugal-compressor plants.



B. ,GRAEMlGER! I OPERATION OF CENTRIFUGAL C(JMPRESSOR PLANTS.

APPLICATION FILED FEB 7; 1916. 1,53,

Emma Apr. 16, 1918.

" rotor wheel or- BENJAMIN GRA'EMIGER, or zumcn,

SWITZERLAND, ASSIGNOR TO THE FIRM or AKTIENGESELLSCHAFT DEB MASCHINENFABRIKEN ESCHER WYSS & 00, 013

ZURICH, SWITZERLAND.

'. ormrrorr or onnrnrruear-comrnnsson PLANTS.

To all whom it may concern:

Be it known that I, BENJAMIN GRAEMI- cm, a citizen of the Republic of Switzerhereby declare the following to be a full,

clear, and exact description of the invention, such as will enable art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to letters or figures of reference marked thereon, which form a part of this specification.

The present invention has reference to an improved method for operating an auxiliary engine in centrifugal compressor plants for moving gaseous media.

. The invention essentially resides in the novelty that the auxiliary engine required for operatin a centrifugal compressor plant is in turn riven by the medium (air or gas) compressed in the compressor, and that this medium is withdrawn from. the compressor at a point in the rear of the second impeller and is conducted back into the-compressor at a point back Ofthe first rotor wheel. Thus, for driving the auxiliary engine a part of the moved a medium is used which has already been gine, necessary need not show unduly large values.

if the compressed to a higher extent than could be obtained by the first rotor wheel, and its tension is reduced in theauxiliary engine only to the pressure obtaining back of. the

thus uses a part of the moved medium of considfirst impeller. The auxiliary engine,

erably lower specific volume than the spefor handling this volume,

This method is especially advantageous medium for'driving the auxiliary engine is withdrawn from behind the last rotor wheel of the compressor and is then reintroduced into the intake space of this last rotor wheel, so that this portion of the I .Theadvantages of the described ste sf- "medi'um describes a cycle which comprises the last compression stage and the auxiliary engine.

may be summed up as follows -For tie purpose of obtainingin the auxiliary turothers skilled in the Specification of Letters Patent. Patented Apr. 16, 1918. Applleatlonfiled February 7, 1918. Seria1-No.-76,7 14. I I

bine low velocity of the motive fluid, conduc'ive to low peripheralspeed of the rotor and thereby simple constructionof this turbine, the drop .of pressure of only one stage of the compressor is made use of. This'in. itself requires a relatively large volume of motivefiuid, and for the purpose of reduc-'- ing this volume and'holdin down the operatlve dimensions of the tur ine, it is of advantage to use only the last pressure stage of the compressor. more advantage as relates to the construction and operation of the compressor on decreasing the volume of moved medium. Because in the auxiliary turbine the pressure of only a few stages, even if only one such, is used, a relatively high percentage of. the total amount of moved medium handled is required for the auxiliary turbine operation. This amount normally remains stationary, no matter whether thecompressor is required to supply much or little com-' pressed medium.

According to the the pressure of the. only that of the very last impeller of the last stage, is to be used, with the result-that the volume of gas handled by the impellers of these last stages, or of the very last impresent invention, only peller thereof, is subjected to very little fluctuation.

Experience has shown that the pump-f ing in airor gas compressors on decrease ofmoved medium does not set in nearly so early,- if in some manner ,care is taken to To this is addedonev igher stages, or even prevent the last stages from reaching the 901 critical supply minimum. The last stages,

then, exert a favorable influence on the preceding stages, as regard thevpumping. ,In-'

asmuch as the last impellers, in the present instance, have to deal with a considerably higher amount of-medium than in prior "methods, their effective cross-sections need not be cut'down to those required by the decrease of the specificvolume, which in the old style compressor, was always regarded 10c withmuch disfavor in shop practice. The portion of the mot1ve medium used by the auxiliaryengine shows the highest into the compressor, act as cooling medium temperatures obtaining in the compressor, T and itcan thus beconslderablycooled-ofl, 10515,

on the air or gas therein, thereby enhancing the efficiency of the compressor. r

The present invention obviates the use of a'special source of power for operating'the auxiliary engine. In cases where formerly the compressor was driven by asteam turbine, generally also'a small steam turbine sure,

gine, but such plants,

was employed for actuating the auxiliary engine for condensing purposes Figures will show that the total steam consumption in the present instance is at least just as favorable as when using an auxiliary steam turbine, which turns its exhaust into the main turbine. Moreover, the air turbine, according to the present proposed method, will be of considerably lighter, simpler and cheaper construction, and can be constructed also for such low output where an auxiliary steam turbine could not be considered. To use an electric-motor in place of a steam turbine is not feasible in many instances for various obvious reasons.

I am aware that pumping plants are already in operation where part of the moved water is used for operating an auxiliary enobviously, cannot anticipate my invention for the reason that there the-waste water is turned back into the intake channel, thatisto say its pressure is reduced to that obtainlng just ahead of the ffirst impeller of the centrifugal pump, and

for the further reason that'there the auxiliary engine has to deal with a motive me dium, the volume of which, no matter what the pressure increase, be affected, so thatthe water plant cannot to a full-degree make use of the advantages, which are the result of my method, deallng with a gaseous, compressible medium.

In the accompanying drawing is shown a plan view, partly in section, of a four stage 1gentrifugal compressor with auxiliary tur- The compressor sucks-in air through the intake 1 and exhausts it through connecting branch 2, with which communicates the condu1t 3 leading part of the air acted on by the lmpelle'r or rotor section 7 to-the rotary auxiliary engine (air turbine) 8, used for instance for driving a cooling water pump 9. The latter sucks the water through connecting branch 10 and discharges it at 11. From the air turbine 8 the spent air is conducted through the connecting branches 12, 12 into the space between the impellers '6 and 7 where it mixes with the newly arrivmg air, compressed by the preceding ir'npellers 4:, 5 and 6, and finally enters again the last impeller. Since for actuating the auxiliary turbine 8 only the, pressure difierence generated the last impeller 7 is used,

the air in passing throughthe passage 13,

with due consideration to the loss of presassumes such a velocity as will best operate asingle, relatively small rotor 14.

will not substantially eoaoee The auxiliary turbine, therefore, is of the utmost simplicity, takes up little space and is cheap to manufacture. For starting the turbine 8 either auxiliary pressure air, provided by a separate compressor or pressure receptacle, or steam may be introduced through the pipe 15. The steam would be exhausted through 16; 'Between the turbine m '5. 6., almost 12,000 kilograms of air and compresses it to 8 atmospheres, at the conduit 3, back of the last impeller 7, 9600 k110- grams of air per hour may bedrawn off for I operating the air turbine 8, which latter drives the condensers necessary for the operation of the compressor turbine.

The weight ratio of the auxiliary air, which is used in a cycle, to the total amount of air moved is=100:80, that is to say, the impellers in advance of the last one 1mpel 100 weight-parts of air, the last impeller will have to impel 180 parts.- If, then, the amount of useful air is reduced to onefourth of its normal value, the last impeller will still have to handle 105 weight-parts and is thus safeguarded against pumping. Relative to the normal rate these 105 parts would be equal to 58% (105:180). As above stated, also the preceding stages would be safeguarded against pumping, notwithstanding that their rate, in the example chosen, would be only 25% of the normal. The internal diameters (efi'ective cross-sections) of the last impeller will have to be enlarged by 80% over plants-where my improvements are not employed. For this reason the last impeller is of such dimensions that the operative passages can readily be work.

Owing to the cycle described by the supply medium between the im eller 7 and the turbine 8, this last impeller has, even on a light load, still to deal with such a large air volume that it-is prevented from pumping or surging and can thus lower the critical limit at which pumping in the preceding stages will be in. 4

The. indispensa le blowing-0d cock 18 communicates by the conduit 19 with the compressor space back of the impeller 6,

with the advantage that by this arrangement .65 times venting compressed medium for'govthe overflow or by pass conduit 21. The blowing-oil air is carried to the rotor 14 of turbine 8 by special guide passages 22. This airthen passes through the conduits 12, 12

' stages, translating the energy of the medium so removed, separately applying the translated energy and returning the medium to 15 a lower pressure stage beyond the initial sta e.

2% In the operation of compressors having a plurality of stages, the method which comprises by-passing compressed medium from a higher to a lower stage beyond the first stage, and translating and separately applying energy of the medium during the passage from stage.

'3. In the operation of compressors having aplurality of stages, the method which comprises discharging compressed medium from a high compression stage into a lower 1 compression stage beyond the first stage,

translating energy of the medium thus "transferred and increasinguthe density of said medium after translation but before entry into said lower stage.

4. In the operation of compressors having 85 a plurality of stages, the method which com prises discharging compressed medium from a high compression. stage intoa lower .com-

pression stage beyond the first stage, translatin energy of the medium while expanding 1t and then coolingthe expanded medium before returning'it to said lower stage.

5. In the operation of compressors having a plurality of stages, the method which comprises discharging compressed medium from the highest compression stage into another compression stage beyond the first stage and translating the energy of the medium during its transfer between the two stages.

6. In the o eration of compressors having a plurality ot stages, the method which comprises discharging compressed medium from a high stage to a lowerstage and translating energy of the medium thus trans- 55 ferred to an extent substantially e uivalent ed to the energy difference of the me tween the two stages.

7 In the operation of compressors having a plurality of stages, the'method which coma continuous dischargeprises maintainm of compressed me ium from a higher sta e to a'lower stage of compression beyond t e -first stage, translating energy of said medium during such discharge, and at prises maintaining a flow of compressed said higher to said lower" erning purposes from the delivery conduit of the highest stage and separately translating energy of' the vented medium.

. 8. In theo eration of com ressors having a a plurality o stages, the met od which comprises discharging compressed medium from a high stage of compression into a lower [compression stage, translating ener of the medium during its passage from t e high to the lower stage and blowing off medium ata stage ofcompression lower than that from which the translated medium is taken,

thereby maintaining the energy in the medium to be translated during. blowing-off periods. l

9. In the o eration of compressors having a plurality 0 stages, the method which comprises discharging compressed medium from a high stage ofcompression into a lower compression stage, translating energy of the medium during its passage from the high to the lower stage and blowing off medium at a stage of compression. lower than that from which the translated medium is taken, thereby maintainin the energy in the medium to be translate during blowing-oil periods, and separately diverting medium from the delivery stream of the compressor and translatingenergy thereof for governing purposes.

10. In combination in a centrifugalcompressor plant, a multi-stage compressor, an

auxiliary machine driven by compressed medium from a highstage of said compressor, and means-to discharge the medium from said machine into a lower stage of the compressor. v

11. In combination in a centrifugal com-' pressor plant, a multi-stage compressor, an auxiliary machine driven from the last stage of the compressor, means to discharge the exhaust medium from sa1d machine into a lower stage of the compressor, and blow-ofi' at that stage of the compressor into which said machine discharges.

12. A- centrifugal. compressor plant, com; prising a multi-stage centrifugal com ressor, an auxiliary machine having an inlet and an outlet and driven by the medium compressed by said compressor, a connection from betweena oint of said compressor beyond at least t e second impeller of said compressor and the said inlet, and a connection between a point of said compressor beyond at least the first impeller of said compressor and said outlet. 13. In combination in a centrifugal compressor plant, a multi-stage centrifugal compressor, an 'auxiliar machine driven by the medium compresse by the compressor,

an inlet and outlet for said machine, a com,

nection between the inlet and a oint situated beyond the last, impeller o the compressor, and a connection between the outlet of the auxiliary machine and a point compressor.

14. In comb nation 1n a centrlfugal compressor plant, a multi-stage centrifugal com pressor, an auxlliary machine,an inlet and"- outlet for said machine, a connection between said inlet and a point situated beyond the last impeller of the compressor, and a connection between but one impeller of the-compressor.

- 15. A centrifugal compressor plant, comprising a multi-stage compressor, and auxiliary machine having an-inlet and an out let and driven by the medium compressed the outlet and a point. situated beyond the last naeaose by said compressor; a connection frombe- 3 goint of said compressor beyondat least the rst impeller of said com ressor and. said outlet, and a cooler interca ter connection. In testimony that I claim the foregoing as my invention,; I have signed my name in presence of two subscribin witnesses. BENJAMIN GR EMIGER. Witnesses ERNST FISCHER, IBER'rHA C. Gnon.

'sor and said inlet, a connection between. a

ated in said lat- 

